1. Field of the Invention
The present invention relates to a treatment tool for an endoscope.
Priority is claimed on Japanese Patent Application No. 2007-029052, filed on Feb. 8, 2007, and Japanese Patent Application No. 2007-119384, filed on Apr. 27, 2007, the contents of which are incorporated herein by reference.
2. Description of Related Art
A treatment tool for an endoscope, such as grasping forceps, for use together with a flexible endoscope, is provided with a coil sheath into which a wire is wound. It is inserted into a body cavity via a treatment tool insertion channel of the endoscope. In this state, in order to revolve the tip end portion of the treatment tool for the endoscope about the axis, an operation portion on the proximal side of the treatment tool for the endoscope is rotated in most cases. Accordingly, treatment tools are known in which a multi wire coil sheath with high rotation transmissibility is arranged so as to improve the rotation following capability of the movable tip end portion.
Here, in the case of a treatment tool such as forceps that is opened and closed by pulling an operation wire from the operation portion, a compression force is loaded in the axis direction of the coil sheath in accordance with the opening and closing. At this time, a multi wire coil sheath into which a plurality of wires are wound has a higher rotation transmissibility compared to a single wire coil sheath into which a single wire is wound, but is more likely to be compressed in the axis direction. As a result, the coil sheath is compressed in the axis direction, which decreases the axial force to be transmitted to the tip end portion. This prevents sufficient treatment, leading to a complicated manipulation. Consequently, there is proposed a treatment tool in which single wire coil sheaths are arranged in multiple layers (for example, see Japanese Unexamined Patent Publication, First Publication No. 2000-229084).